Kirby's drive to be her best led her to this man -- James Arthur Ray -- a charismatic self-help author who spread an appealing message in his motivational DVDs.

Ray’s philosophy is based on something called the law of attraction. Simply put, if you send positive energy out into the world around you, Ray said you would attract positive things in return, like more money, better health, and a happier life.

JAMES RAY: You've got to be at the right place, at the right time, and do the right things, get the right opportunities, make the right decisions, meet the right people, and get the right results and that's when all the laws line up behind you and you really begin to have this magical life.

His upbeat message struck a chord. Ray conducted seminars across the country, and wrote books. But it was this project in 2006 that catapulted him onto the national stage.

He became one of the voices behind the hugely successful motivational book and DVD "The Secret."

James Ray, from “The Secret” DVD: That’s not who you are, that’s who you were.

“The Secret” book and DVD sold more than 10 million copies and landed James Ray at the Holy Grail for any motivational speaker -- an appearance on Oprah.

MELINDA MARTIN: They put keys on the bottom of these giant aquariums full of snakes. And these snakes were just going crazy trying to escape. And people had to put their hands inside and grab one of these keys. And people were crying and shaking. It was really something.

Still, Melinda says it all seemed harmless enough. She saw the participants as smart people who wanted to push themselves to the next level.

MELINDA MARTIN: They would graduate and get more extreme as you followed these events. Probably the most challenging event was “spiritual warrior.” This was the extreme of the extreme, this event.

According to James Ray, the spiritual warrior retreat would push the participants beyond their perceived limits. Of all his events, this one was the most challenging - mentally, emotionally and physically. He encouraged those who came to "be courageous" -- and prepare for a life-altering event.

DENNIS MEHRAVAR: Mr. Ray always says that this is his best material, this is his best work.

If the spiritual warrior retreat was one of Ray's best events, it was also one of his most expensive -- almost $10,000. Ray would lead the five day event in Sedona, at a rented facility called Angel Valley Retreat Center, owned by Amayra Hamilton.

AMAYRA HAMILTON: A lot of people carry burdens. And being here helps people to drop the burdens. They become free to be themselves.

Businessman Dennis Mehraver signed up, along with about 50 people, including orthodontist Beverley Bunn, who would be paired up as roommates with Kirby Brown.

CHRIS HANSEN: Did you feel a special bond with her?

BEVERLY BUNN: Right away. And Kirby smiles the whole entire time. You have to understand. She's beautiful.

Also heading to Arizona was Marta Ries.

Marta had been attending James Ray workshops for years and was now working for Ray part-time, helping him with his audio-visual presentations.

Yet to her surprise, Beverley not only made it through, she enjoyed it.

CHRIS HANSEN: What did you do during that 36 hours?

BEVERLY BUNN: Actually, I have an extremely, extremely busy life. So, for me to be able to sit and do nothing, it was a great experience.

There was just one day left. What else was in store for James Ray's spiritual warriors?

On the Sedona property was a tent called a sweat lodge.

Inside, Ray would lead a ceremony loosely based on a Native- American ritual, a kind of steam bath meant to symbolize re-birth.

DENNIS MEHRAVAR: He asked, "Has anybody been in a sweat lodge before?" I would say probably maybe eight or nine people raised their hands. And then his comment was, "well, you've never been to my sweat lodge."

Ray promised that his sweat lodge would be like nothing they'd ever been through before. And it was. Just not in the way any of them imagined.

Nestled in the red valleys of Sedona, James Ray's spiritual warrior retreat had reached its final day.

After their 36-hour fast in the outdoors, participants arrived back at the retreat center to find breakfast waiting. And there was one final challenge: the sweat lodge ceremony.

Sweat lodge ceremonies are traditionally seen as purification rituals, although Ray's version was billed as a test of endurance.

DENNIS MEHRAVAR: Before we went, Mr. Ray said that you're going to feel like your skin is coming off.

But what these participants may not have known was that there'd been at least one problem in the past. Property owner Amayra Hamilton remembers that back in 2005 one man emerged from the sweat lodge completely disoriented.

AMAYRA HAMILTON: He was moving and we could not calm him down. And thought, "Unh-uh (negative). This needs help."

What struck Amayra at the time, she says, was Ray's reaction when she decided to call 911.

AMAYRA HAMILTON: I said to James, "This-- this guy is-- is not okay. I'm calling-- going to call 911." And he didn't like that. I said, "I’m going to do it anyway." So, I called 911--

CHRIS HANSEN: Did he tell you not to call 911?

AMAYRA HAMILTON: Mmmm--he said, "Well, why would you do that?" and I--

CHRIS HANSEN: Why would you do it?

AMAYRA HAMILTON: Something like that.

A source close to James Ray says that's not how it happened, and that disoriented participant turned out to be fine.

In the following years Ray did make some changes.

He shortened the ceremony, and kept fruit and water on hand to help with dehydration.

With a series of chants, Ray doused them with water, filling the tent with steam.

DENNIS MEHRAVAR: I mean, the stones were hot.

CHRIS HANSEN: Is the perspiration just--

DENNIS MEHRAVAR: Oh--

CHRIS HANSEN: Pouring off you?

DENNIS MEHRAVAR: It's just-- like-- I’ve never experienced anything like that. I mean, it's so hot that you're soaking wet in the first, like, first two minutes, first one minute. It's very intense.

Ray's event coordinator Melinda Martin was outside. It was her first time working the sweat lodge ceremony.

MELINDA MARTIN: The job was, "Yes. When people come out they're going to be hot and they're going to be dehydrated. So, you just hose them down and give them some electrolyte water, and then, like, in ten minutes they're totally fine."

It was dark and steamy inside the lodge until Ray propped open a flap to signify the end of round one. But Dennis felt no relief at all.

DENNIS MEHRAVAR: Looking at the opening, I see the light that is coming in a little bit. But there is no air. I mean, you couldn't breathe. There was no oxygen here. Imagine, like you are just cooking. We were just cooking.

For their own safety, Ray encouraged the participants to leave only between rounds.

DENNIS MEHRAVAR: Well, he said, "you are bigger than that, you are better that."

MELINDA MARTIN: The flap opened and the first group of people came out I was very surprised at how bad the condition of these people was already. These people--they don't look healthy at all. They look like they're really suffering, you know. And that was just the first round.

Inside: more hot stones, more steam.

DENNIS MEHRAVAR: By the time the-- fourth round start, I remember I was just kind of laying close to the ground, trying to cool off a little bit.

CHRIS HANSEN: You were all grown-up. You could have all gotten up and said, "We're out of here. This is dangerous, we're feeling ill."

DENNIS MEHRAVAR: Um, hm. Well, I guess my answer would be that you are soaked in that material listening to him 13 hours a day for four or five days, little sleep, so your judgment is different than me sitting here.

Dennis says his better judgment did kick in about half way through the ceremony.

He showed us what happened next, when he made a split -second decision to get out.

DENNIS MEHRAVAR: I thought, "Oh, you know, I can't do this." And probably I moved from here to--probably just like this.

CHRIS HANSEN: Right. You were about to make your way around the fire pit--

Unconscious, Dennis assumes he was dragged out. The next thing he remembers was being hosed off on the ground, vomiting, unable to move.

And then it got worse.

DENNIS MEHRAVAR: I’m trying to breathe and I can't breathe. So I take, like, say, 10 breaths [pants] but I don't-- it's as if I’m-- nothing's happening.

CHRIS HANSEN: Nothings coming in?

DENNIS MEHRAVAR: And I start to see this black spots on my vision like, I’m trying to stay up, I try to-- trying to fight it, and at that time, I mean, I start to say, "I don't want to die, not here, not now." I have two kids, they don't know I’m here, that, you know, they're waiting for me to go back. I’m just saying, "Jesse, Jordan, I don't want to die. I don't want to die here, I have two kids.” I’m yelling their name as loud as I can, Chris.

Was this the rebirth James Ray had promised or the start of something tragic?

Halfway through James Ray's sweat lodge ceremony, Dennis Mehraver had been dragged out unconscious.

He came to thinking he was about to die.

MELINDA MARTIN: He was hysterical. He was screaming and saying he had a heart attack. And just screaming at the top of his lungs. It was terrifying. Terrifying.

The ceremony still had another hour or so to go but Marta Reis-- the part-time Ray staffer-- wasn't as alarmed.

From past experience, she says it's not unusual to leave a sweat lodge feeling out of sorts, and in what she calls "an altered state."

MARTA REIS: You are definitely, you know, disoriented. You might even, you know, say a few things that don't make necessarily sense to the people that are there.

But this was event coordinator Melinda Martin's first time at a James Ray sweat lodge, and to her the scene was increasingly disturbing.

She saw one man emerge with serious burns , having brushed against the hot rocks on the way out.

MELINDA MARTIN: From here all the way down all the skin was gone. The skin was gone. His knees, there was, like, no skin. It was just horrible. But he was also very delusional and was so concerned about leaving sweat lodge too early and letting James down. He kept saying, “I’ve got to finish it. I've got to play full on."

Beverley Bunn was inside the lodge next to her roommate Kirby Brown when she decided she'd had enough.

BEVERLY BUNN: I went from where I was. And got to a kneeling position and started to crawl towards the door. And James was sitting there. Right at the door. He said, "You are definitely stronger than this. You're stronger than this. You can overcome this. It's mind over matter.”

So Beverley stayed, in a spot near Ray--close to the door-- where there was a little more air.

That's when she and the others saw a beam of sunlight enter the tent from the back. One participant had lifted the outer covering.

BEVERLY BUNN: He was out of control. I can’t take it anymore, can’t take it anymore.

CHRIS HANSEN: He was having a panic attack?

BEVERLY BUNN: He was freaking out. He was having a panic attack. He lifted up the back of the tent and he went out. And then James Ray was like, "Where's the light coming from? What's happened?" And then he actually reprimanded that person, but he also let us know that it was a sacrilegious act.

BEVERLY BUNN: Yeah. And he went back to where he was and because of that, people started calling out each other's names. And they just started randomly calling each other's names. But there was-- it was such chaos in there that nobody knew who was being called or who was calling you. Or if any of--everybody's name got called or if anybody answered. You just couldn't tell.

CHRIS HANSEN: And could you even see?

BEVERLY BUNN: You couldn't really see.

CHRIS HANSEN: What was James Ray doing during all of this?

BEVERLY BUNN: He again encouraged people to keep on going. “I'm stronger than this.” Tells everybody when the chaos is going on. "Quiet down. Quiet down."

CHRIS HANSEN: “Quiet down.”

BEVERLY BUNN: “Everybody-- I’m in charge of this. And everybody needs to be quiet." And so--

BEVERLY BUNN: Every-- people are throwing up. People are spitting. It's-- yeah, it's very, very chaotic in there.

MELINDA MARTIN: In addition to the regular chanting and stuff he would say, "You're stronger than this. You can do this. You think you're going to die. You're not going to die. Fight through the pain.” You can hear him very strongly saying that from the outside.

Whether trying to please James Ray, or trying to prove something to themselves, most kept going.

And by the final round, after nearly two hours of mind over matter, the chaos had given way to silence.

BEVERLY BUNN: It was quiet. And no one said anything. But I also think that there was some more people that were passing out. And I don't by that time, people couldn't speak for themselves. They just couldn't speak anymore.

When the ceremony ended, James Ray told his warriors it was time to leave. As Beverley made her way out, she heard a strange sound coming from her roommate Kirby Brown.

BEVERLY BUNN: I hear this snoring sound. I hear a [snorts] sound. And I’m looking. And I know where Kirby was sitting. And Kirby was laying there. And the sound is coming from her. And it was a snoring sound. And I thought, "Kirby’s passed out."

Outside the tent, Dennis was catching his breath-- still too weak to move on his own-- when he saw James Ray.

DENNIS MEHRAVAR: He was like smiling as if like, you know, it's finished, it's good. I was halfway up and kind of-- he helped me out and give me a high five. And I said, "James, I think I died." And he says, "Yeah, you were reborn-- reborn."

CHRIS HANSEN: Reborn?

DENNIS MEHRAVAR: Reborn. So go take a shower and get ready for dinner.

But within minutes, she says, Ray and the other sweat lodge veterans realized something had gone drastically wrong.

MARTA REIS: Someone said there's still people in there. Some people were becoming very frantic. They're not moving, this and that. And that's when we sort of ripped open one of the sides of the sweat lodge and we pulled James Shore out. We pulled Kirby out. And then I immediately performed CPR on James.

Property owner Amayra Hamilton rushed to the scene.

CHRIS HANSEN: Were you prepared for what you saw?

AMAYRA HAMILTON: Chris, what I saw was beyond anything I’ve ever seen. People collapsing, people falling over, people vomiting, people -- horrible.

AMAYRA HAMILTON: Oh, he was standing there. I thought, "Well, maybe he's one of those people that just gets paralyzed and doesn't know what to do in a situation like that."

CHRIS HANSEN: Did you say anything to him?

AMAYRA HAMILTON: No. You know, we had an interaction. A couple years before that I had called 911 without his approval. And this time I thought, "This is way beyond anything—any previous situation.”

While waiting for emergency responders to reach the secluded site, the able-bodied did what they could.

One of Ray's "Dream Team" volunteers was also a registered nurse. And Melinda Martin had been trained in CPR when she joined the company.

MELINDA MARTIN: At first we had them on the tarps, and pretty soon there wasn't enough room on the tarps. People were just lying on the ground. You know, I was turning people on their sides so they didn't choke on vomit. It was incredible.

BEVERLY BUNN: I’ve never been a participant in a plane crash. But it would be-- it's like a disaster. A triage center. Or a plane crash. Without the plane.

She searched for her friend and roommate Kirby Brown.

BEVERLY BUNN: And I look through the tent. And I could see through the door to the other side. And I see Kirby’s stomach going up and down and I know they're doing CPR.

And Marta Reis discovered her friend Liz Neumann unconscious.

Marta Ries: I was just basically talking to her and saying "I’m here. I'm here. Follow my voice back. I'm here to help you." And I just kept stroking her arm. I didn't care if it was silly. I didn't care if it was stupid. I was going to do something.

CHRIS HANSEN: You've got EMS arriving.

AMAYRA HAMILTON: Yes.

CHRIS HANSEN: You've got choppers coming in.

AMAYRA HAMILTON: Yes.

CHRIS HANSEN: Any point did you stand back and say, "Oh my god, how did this spin so horribly out of control?"

AMAYRA HAMILTON: Of course, it tears you apart that something this outrageous seems to happen in the place that our focus is on peacefulness and on harmony and on balance and quiet.

James Ray's spiritual warrior retreat ended with more than a third of the participants being rushed to the hospital.

The last time Ginny Brown had seen her daughter Kirby, she was all smiles ... And gearing up for her big adventure at the James Ray spiritual warrior retreat.

CHRIS HANSEN: Ginny, how did you hear that something had gone tragically wrong in Sedona?

VIRGINIA BROWN: A trooper came to our door. Asked if we knew Kirby Brown. I-- he just said, "your--" You know, I said, "I’m her mother." And he said, "your daughter has passed in a sweat lodge in Sedona, Arizona." I don't exactly remember what happened.

CHRIS HANSEN: And did they say how she died? Why she died?

VIRGINIA BROWN: You know initially we just thought some terrible tragic accident.

Kirby Brown died from heat stroke on the afternoon of the sweat lodge. As did James Shore, the father of three who'd pulled an unconscious woman out of the lodge before passing out himself.

And days later, Liz Neumann -- the Ray volunteer who'd followed his teachings for seven years -- died in the intensive care unit.

Back at the retreat center, some participants waited for James Ray to help them make sense of what had just happened.

BEVERLY BUNN: Most of us stayed up all night talking. And trying to figure out, you know, what is James going to do? When is he going to come and talk to us?

CHRIS HANSEN: So, you thought he would come back and at least have a conversation.

BEVERLY BUNN: At least have a conversation, at least say a prayer. At least say, "I’m sorry that this happened. And this is what we have to do. Advise us, guide us, be our leader." That's what he's been for the whole week.

But James Ray did not call a final meeting to mark the tragic end of his warrior retreat.

Ray also never visited the hospitals where the injured and dying had been taken.

He left Arizona the next morning.

BEVERLY BUNN: That part, I won't get over.

Dennis Mehravar was treated at the hospital for extreme dehydration and was surprised not to see Ray there.

CHRIS HANSEN: What does that say about James Ray?

DENNIS MEHRAVAR: Well, Chris, that's exactly where I start thinking that maybe the man I followed for the last three, four years is not the man that he says he is.

But by then Dennis was focused on just one thing: flying home and hugging his two sons.

DENNIS MEHRAVAR: It was the best day. And of course they don't know what happened to me so I’m, you know, holding them and kissing them and I don't want to let go of them. And they're probably thinking, wow, dad is being a little bit weird.

In the coming days, Ray did reach out to the family of Kirby Brown. But they say the gesture was too little, too late -- and then some.

VIRGINIA BROWN: Someone from his organization should have been on my stoop-- on my porch that Friday morning holding my hand. Someone from his organization should have been making the arrangements.

JAMES RAY: It's okay to grieve, it's okay to be confused. I'm confused. I feel frustration, and I feel grief and yet in the midst of that you got to do the things that take care of you which is going to make you better and it's going to keep you healthy and it's going to keep you moving forward and that's best for every single one of our family members who might still be ill or in the hospital or those families that of the deceased.

But for Beverley Bunn at least the call backfired.

She was furious when one of Ray's volunteers described a ceremony that had been held at the sweat lodge site. A psychic claimed to have communicated with the deceased and supposedly had this to say:

[phone call]

James Ray volunteer: She said that they had left their bodies during the sweat lodge, and that they were having so much fun that they chose not to come back. That was their choice that they made.

BEVERLY BUNN: They were having more fun in this other life.

CHRIS HANSEN: Almost like they chose to die?

BEVERLY BUNN: Correct.

CHRIS HANSEN: How'd you react to that?

BEVERLY BUNN: I put my phone on mute. And I just cried. Because I couldn't believe what I was hearing. But the bad vibes among some participants were quickly becoming the least of James Ray's problems.

Detectives from the Yavapai county Sherriff’s department had launched a full-scale investigation.

Was there evidence to charge Ray with a crime? Had he created an unsafe environment, and then done nothing when it was clear the situation had turned deadly?

DENNIS MEHRAVAR: I think he just wasn't prepared for it and when it happened, he just ignored it.

Ray's event coordinator Melinda Martin was so horrified and confused by what happened, she never returned to work.

MELINDA MARTIN: I don't know who's to blame for anything. I mean, I don't think anybody intended for this to happen, that's for sure.

While the Sherriff’s department was working the case, James Ray hired a team of lawyers to do his own investigation. The result is this document they call "the white paper" which denies any negligence whatsoever.

In it, Ray's lawyers say he took extensive precautions and could never have predicted what they describe as a tragic accident.

Ray's attorneys point out that all the participants had been warned of the risks in releases they signed.

And other than the 36 hour fast, they had been repeatedly told to hydrate.

What's more, they say no one was forced to stay inside the lodge -- and at least 16 people did leave. Ray calls his participants "educated, tough people" who should have known "their own limits" and been able to "take care of themselves."

Marta Reis, who worked for Ray part-time and was outside the sweat lodge on the day of the tragedy, says no one had to take part.

MARTA REIS: Nobody's telling them to stay in. Nobody's telling them to go out. They're doing it the way that they want to do it.

VIRGINIA BROWN: I don't think she could. And I think she would have believed him saying, "Don't pay attention to how you feel. You will be fine. This is not a problem."

Ray's attorneys liken his encouragement inside the lodge to a coach cheering on a marathon runner.

It's a comparison Kirby Brown's family rejects.

ROBERT BROWN: I ran a marathon. And you know what I didn't do before a marathon? I didn't sit in a desert for 36 hours without food and water. And when I ran a marathon there were paramedics there. If I passed out somebody was right there to help me. This was not a marathon. This was something that he put these people through recklessly.

But exactly what went wrong is still in part a mystery: there was no thermometer inside the tent, so no one's sure how hot it got or why some people died when others emerged virtually unscathed.

Ray's lawyers have suggested there might have been a design flaw in the lodge-- a structure that Ray's company did not design, build or maintain.

It has since been torn down and the site has been turned into a memorial.

He says he and his employees had "no idea of the seriousness of the problems" until the ceremony was over. Had they known, Ray says, they would have stopped.

But on this critical point, Beverley Bunn tells a different version of events.

She says Ray was aware that at least one woman was in serious trouble.

BEVERLY BUNN: At the sixth round is when you hear, "She's passed out. She's passed out. Can't get her to breathe. I don't know if she's breathing." And by then, by the time we heard that, the rocks had been brought in. And he closed the door. And he actually acknowledged it. And he said, "the door's now closed. This round has begun. And we'll deal with that at the end of this round."

CHRIS HANSEN: Deal with what?

BEVERLY BUNN: The person that's passed out.

CHRIS HANSEN: So, he starts another round knowing that there's a woman unconscious in the sweat lodge?

BEVERLY BUNN: Yes.

In February, Ray was arrested and charged with three counts of manslaughter.

He's pleaded not guilty and is free on bail while awaiting trial.

Ray is also in talks with the Browns and some participants -- including Dennis and Beverley -- about a financial settlement.

Dateline wires the home of a volunteer, Jenny, from top to bottom with hidden cameras. Then she called repairmen to her house for a simple problem we created as a test with Jenny's pool. NBC's Chris Hansen reports.